Metal forming machine and wire preheating apparatus



Nov. 24, 1970 J. F. LOFTUS ETI'AL 3,541,832

METAL FORMING MACHINE AND WIRE PREHEATING APPARATUS Filed 001;. 21, 1968 2 Sheets-Sheet 1 INVENTORS JOSEPHELOFTUS V/NCENTASTA/VTON afforneys Nov. 24, 1910 LOP-ms ETAL 3,541,832

METAL FORMING MACHINE AND WIRE PREHEATING APPARATUS Filed Oct. 21, 1968 2 Sheets-Sheet 2 INVENTORS JOSEPH F LOF TUS b V/NCENTASTA/VTO/V attorneys Patented Nov. 24, 1970 3,541,832 METAL FORMING MACHINE AND WIRE PREHEATING APPARATUS Joseph F. Loftus, Torrington, and Vincent A. Stanton,

Canton, Conn; said Loftus assiguor to The Torriugton Manufacturing Company, a corporation of Connecticut Filed Oct. 21, 1968, Ser. No. 769,145 Int. Cl. B21d 7/ 16 US. Cl. 72364 17 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Preheating of wire for stress relief has been accomplished in the past, as for example in US. Pat. No. 2,219,- 376Leonard A. Young et al. entitled, Method of Manufacturing Coil Springs, By Means of Electrical Resistance Heating. Such preheating has not, however, been wholly satisfactory and particular problems have arisen in the case of wire forming machines having nonuniform feed rates, i.e., intermittent stop and go feed movements, variable speed feed movements, etc. With the wire stopped, rapid overheating can occur in the case of resistance heating and close control over wire temperature is extremely difficult if not impossible in the absence of complex closed-loop electronic controls. In resistance preheating, it is extremely diflicult if not impossible to accommodate copper and a whole family of resistance alloys which tend toward excessive overheating in the absence of extremely close control. Wire which is coated for eX- ample with oil, phosphate, borax, lime, and oxide type coatings or wire which may be contaminated is not readily accommodated in resistance preheating.

SUMMARY OF THE INVENTION It is the general object of the present invention to provide improved wire preheating means usable to particular advantage in combination with wire forming machines Which accommodate a continuous length of wire and which exhibit a nonuniform wire feed rate.

In fulfillment of this object, a container means is provided for holding a quantity of a liquid wire preheating medium and a simple yet effective heater and control apparatus maintains the liquid medium and the wire at a desired temperature. A guide means preferably comprises a tubular member having openings for the entry of the liquid medium into direct heat exchange contact with the wire and is adapted to position a section of the wire selectively in and out of the liquid medium. With this straight forward approach, a high degree of efiiciency in heat transfer is achieved and precise temperature control can be accomplished in the absence of complex electronic or other control elements. The problem of overheating can be obviated merely by maintaining the liquid medium substantially at the desired wire temperature. Thus, nonuniform feed rates pose no problem. Similarly, coatings or contamination on wire do not significantly effect heat transfer efficiency. Effective forming is achieved and heat treated springs or other formed articles may be taken directly from the forming machine.

Optionally, electrical resistance or other heating may be employed prior to the liquid medium preheating for rapid temperature increase in the wire and the liquid medium may be employed for stabilization and close control of temperature. Further, wire between the liquid medium and the work station of the forming machine may be heated electrically for maintenance of a desired temperature level and, in the case of electrical resistance heating, it is contemplated that one electrode may be located immediately adjacent the work station for delivery of Wire at a precise desired temperature to the work station. It is anticipated, however, that in the majority of cases liquid medium preheating alone will sufiice in providing the desired heating and temperature control of the wire.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration showing a spring coiler and a liquid medium preheating apparatus constructed in accordance with the present invention.

FIG. 2 is an enlarged vertical section showing the liquid medium preheating apparatus in greater detail.

FIG. 3 is an enlarged vertical section taken generally as indicated at 3, 3 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT As mentioned above, the present invention is directed particularly to metal forming machines having nonuniform feed rates. Thus, the invention finds particular utility in the case of segment type spring coiler having an intermittent stop and go wire feed movement but no limitation is contemplated as to such specific nonuniform feed rate. Further, various other metal forming machines are contemplated such as spring winders, four slide machines, etc., which accommodate a continuous or indeterminate length of wire advanced thereto from a coil or other source. The term wire is also used in a broad sense and is intended to include continuous or indeterminate lengths of any cross section such as circular, rectangular, irregular, etc.

Referring now particularly to FIG. 1, it will be observed that a spring coiler is identified therein at 10' and has the usual arbor 12 and abutment 14 at a work station 16. Feed rolls 18, 18 advance wire 20 to the work station 16 and are rotatable intermittently, springs being formed and severed successively at the work station in the conventional manner. Wire passes to the feed rolls 18, 18 through a conventional straightener 22 and is supplied from a source in the form of a coil 24. A wire preheating means or apparatus is indicated generally at 26 between the coil 24 and the spring coiling machine 10 and comprises a container means 28, a liquid wire heating medium 30 therewithin, and a wire guide means 32. As best illustrated in FIG. 2, the container means 28 comprises an inner container 34 for holding the liquid preheating medium 30 and a fire brick liner 36 extending thereabout. The container means also includes heater and control apparatus for raising the temperature of the liquid 'wire heating medium and for maintaining said temperature at a desired level. Such means may vary widely but is shown in the form of resistance wire heaters 38, 38, a thermocouple 40, and a thermostat 42. The thermostat 42 is shown in broken line connection with the heaters 38, 38 and the thermocouple 40 and operates in a conventional manner to maintain the liquid medium at a desired temperature level.

As mentioned above, the liquid wire heating medium may comprise a salt, tin, lead bath, etc. and has the inherent characteristic, when in direct contact with the wire, of providing a highly efficient and rapid heat transfer condition.

In preferred form the guide means 32 comprises a tubular member through which the wire passes and which is provided with at least one opening for the ready entry and egress of the liquid heating medium, the medium thus being brought into direct heat exchange contact with the wire. Further, the tubular member is preferably adapted for selective positioning of at least a portion thereof in and out of the liquid heating medium. As shown, the guide member 32 has axially spaced portions 44, 44 entered in suitable openings 46, 46 in the container 34 for relative movement with respect to the container. That is, the portions 44, 44 of the guide member are rotatable or at least swingable through a limited angle in the openings 46, 46 for corresponding swinging movement of a radially off set intermediate portion 48 of the guide member. The intermediate portion 48 has a series of small openings 50, 50 for entry and egress of the liquid heat ing medium and, it will be apparent, that appropriate swinging movement of the guide member can be affected to selectively position the portion 48 in and out of the liquid medium. It may, for example, be convenient to swing the guide member to remove the wire in the member portion 48 from the liquid medium for overnight shut down, etc.

In an illustrative embodiment, a tin bath is employed as a liquid medium and is maintained at a temperature between 600 and 700 degrees Fahrenheit (600 F.700 E). Such temperature is slightly higher than the normal stress relieving temperature for the wire employed .028 (twenty-eight thousandths) diameter phosphate coated music wire, and the temperature at the work station 16 in the spring coiler is, of course, slightly lower than at the bath. Wire feed is at the rate of 300 feet per minute through a one and one-half (1 /2) foot immersion in the bath and approximately 160 springs per minute are formed with excellent results. Baths, temperatures, feed rates, etc., will of course vary with the Wire accommodated aud the articles formed. It is to be noted, however, that substantially shorter lengths of wire immersion have been contemplated than have heretofore been thought possible in hotbath treatments of strings, wire, etc., for other purposes. Due to the excellent heat transfer characteristics of the hot bath-wire in direct contact with each other extremely rapid heating occurs despite movement of the wire at substantial feed rates. It is believed that a most important parameter in determining length of wire immersion is the ratio of heat flow through a unit of surface area of the wire relative to the thermal mass associated with that area. Even with the wire up to inch diameter, it is believed that a bath of sufficient length to provide for a wire immersion length of four (4) feet will provide the necessary preheating at practical wire feed rates in the neighborhood of 100 feet per minute. The bath heater and control apparatus in all cases are constructed and designed of such size and capacity particularly as to bath width, depth, etc., and heater capacity to prevent any appreciable temperature loss in the bath as a result of heat transfer to the wire.

Optionally, electrical resistance or other heating may be combined with the liquid medium preheating. Thus, reverting to FIG. 1, heating may be accomplished at the coil 24 or between the coil and the preheating apparatus 26 by electrical resistance or other methods, such heating being particularly desirable when the length of the apparatus 26 might otherwise be excessive as with very large diameter wire. Electrical resistance heating is shown with electrodes 52, 52 provided between the coil 24 and the apparatus 26 and it is contemplated that such heating will effect a rapid rise in wire temperature with stabilization and close control of wire temperature effected by the apparatus 26. Electrical resistance or other heating between the apparatus 26 and the work station 16 may be desirable in certain cases as illustrated by electrodes 54, 54, maintenance of wire temperature between the apparatus 26 and the work station thus being achieved. In the alternative, the left-hand electrode 54 may be replaced by an electrode 54a in close proximity to the work station 16 for maintenance of wire temperature levels im- 4 mediately prior to forming. Addition of a limited amount of heat in such manner for post bath temperature maint nance does not pose problems of sophisticated and expensive control means. Further, prebath heating may be roughly controlled since the bath will heat or cool as necessary.

We claim:

1. The combination comprising a metal forming machine adapted to receive and to operate upon a continuous length of wire and which includes a feed mechanism and a work station, the feed mechanism operating to advance the wire to the work station at a nonuniform rate of movement, a source of wire connected with the feed mechanism and disposed in spaced relationship therewith and with wire extending therebetween, and a wire preheating means disposed between said forming machine and said wire source in operative association with the wire extending from the source to the feed mechanism, said preheating means comprising a container means, a liquid wire heating medium therein, and a wire guide means, said container means including heater and control apparatus for raising the temperature of said liquid wire heating medium and for maintaining said temperature at a desired level for stress relief, and said wire guide means receiving wire from said source and discharging the same toward said feed mechanism and maintaining a section of said wire in direct heat exchange contact with said liquid heating medium.

2. The combination as set forth in claim 1 wherein said wire guide means is adapted selectively to maintain said wire section in and out of direct heat exchange contact with said liquid heating medium.

3. The combination as set forth in claim 2 wherein said wire guide means comprises a tubular member through which the wire passes and which is provided with at least one opening for the entry of the liquid heating medium, the said tubular member being adapted for the selective positioning of at least a portion thereof in and out of the liquid heating medium.

4. The combination as set forth in claim 3 wherein said tubular guide member has axially spaced portions swingably supported by said container means and an intermediate portion Which has a plurality of small openings and which is offset radially with respect to said axially spaced portions so as to swung selectively into and out of said liquid heating medium in said container means.

5. The combination as set forth in claim 1 and including an electrical wire heating means disposed between said preheating means and said wire source, said electrical heating means being adapted for rapid wire heating and said preheating means serving to stabilize and to closely control wire temperature.

6. The combination as set forth in claim 1 and including an electrical wire heating means disposed between preheating means and said work station on said forming machine, said electrical means serving to maintain wire at a desired tempearture after it is discharged from said preheating means.

7. The combination as set forth in claim 6 wherein said electrical wire heating means is of the resistance type and comprises at least two electrodes one of which is arranged closely adjacent said work station.

8. The combination as set forth in claim 6 and including an electrical wire heating means disposed between said preheating means and said wire source.

9. The combination as set forth in claim 1 wherein said container means and wire guide means is constructed and arranged to provide for a length of wire immersion no greater than four (4) feet.

10. The combination as set forth in claim 9 wherein said container means and wire guide means is constructed and arranged to provide for a length of wire immersion no greater than two (2) feet.

11. The combination as set forth in claim 10 wherein said container means and wire guide means is constructed and arranged to provide for a length of wire immersion approximately eighteen inches long.

12. The combination as set forth in claim 1 wherein said liquid heating medium takes the form of molten tin.

13. Wire preheating apparatus for use with forming machines having a nonuniform feed rate, said apparatus comprising a container means and a liquid wire heating medium therewithin, said container means including heater and control apparatus for raising the temperature of said liquid wire heating medium and for maintaining said temperature at a desired level, and a guide means for receiving a continuous length of wire and discharging the same to said forming machine, said guide means being provided with at least one opening for the entry of the liquid heating medium into direct heat exchange contact with the wire, and said container means and guide means being constructed to provide for a wire immersion length no greater than 4 feet.

14. Wire preheating means as set forth in claim '13 wherein said immersion length is less than two (2) feet.

15. Wire preheating means as set forth in claim 14 wherein said immersion is approximately eighteen inches.

16. Wire preheating apparatus as set forth in claim 13 wherein said guide means comprises a tubular guide member with axially spaced portions swingably supported by said container means and an intermediate portion which has a plurality of small openings and which is olfset radially with respect to said axially spaced portions so as to be swung selectively into and out of said liquid heating medium in said container means.

17. Wire preheating apparatus as set forth in claim 13 wherein said liquid heating medium takes the form of molten tin.

References Cited UNITED STATES PATENTS 15,899 10/1856 Perkins 72-128 1,096,866 5/1914 lSchinnerling 72364 2,505,623 4/1950 McLaughlin 72128 2,511,274 6/1950 Kramer 72l28 LOWELL A. LARSON, Primary Examiner US. Cl. X.R. 72-128 

